Although the immunohistochemical data were consistent with an ordinary atherosclerotic aortic aneurysm, in which TCR Valpha-Vbeta gene usage is known to be polyclonal, the restricted TCR gene usage suggests that a certain autoimmune mechanism was involved in the pathogenesis of this case similar to Takayasu's arteritis, in which massive infiltration of delta T lymphocytes and strong expression of HSP-65 in the aortic tissue are characteristic.